An early concept of end-to-end (E2E) verifiable voting systems, designed to provide both transparency and privacy in elections. One of the most well-known examples of this type of system is called Prêt à Voter (French for “Ready to Vote”), introduced by David Chaum, a pioneer in cryptographic voting.

Here’s a high-level breakdown of how it works:

Core Concepts

	1.	Paper Ballots with Encrypted Codes: Each voter receives a ballot with a list of candidates and an associated encrypted code. The code corresponds to the voter’s choice but is encrypted so that no one, not even the election officials, knows the chosen candidate directly.
	2.	Separation of Choice and Identity: After marking their choice, the voter tears off a part of the ballot, keeping their selection and a unique encrypted identifier or code. This part of the ballot can be used later to verify that their vote was correctly recorded without revealing which choice they made.
	3.	Cryptographic Verification: Once the votes are counted, a list of encrypted codes (not the candidates themselves) is published online. Voters can verify that the code associated with their vote appears on this list, proving that their vote was correctly recorded. Only the voter can link this code to their actual choice, preserving privacy.
	4.	Auditable Transparency: To detect manipulation, independent auditors can verify that the encrypted votes were properly processed through cryptographic proofs, and that the final tally matches the published codes. This process uses a type of zero-knowledge proof, which allows verifying a truth without revealing any actual private data.

Advantages

	•	Transparency and Trust: The system offers verifiable assurance that all votes are counted accurately, with tamper-evidence at every step.
	•	Privacy: Voters verify their vote was recorded without disclosing their choice to anyone else.
	•	Security: Since the system relies on cryptographic proofs, it’s difficult for an attacker to alter the outcome without detection.

Later Innovations

Other similar systems include Scantegrity (used in Takoma Park, Maryland, in 2009), which also employed a verifiable optical scan system, and Helios, an online voting system used in smaller-scale elections that combines E2E verifiability with digital-only ballots.